May 9, 2006 -- Thyroid cancerThyroid cancer diagnoses more than doubled in the U.S. from 1973 to 2002, and a pair of researchers think they know why.
"The increasing incidence of thyroid cancer in the United States is predominantly due to the increased detection of small papillary cancers," write Louise Davies, MD, MS, and H. Gilbert Welch, MD, MPH.
Despite the rise in U.S. thyroid cancer diagnoses, the nation's thyroid cancer death rate held steady from 1973 to 2002, note Davies and Welch. They work at the Department of Veterans Affairs Medical Center in White River Junction, Vt.
Their study appears in The Journal of the American Medical Association.
About Thyroid Cancer
The American Cancer Society predicts about 30,180 new diagnoses of thyroid cancer and 1,500 thyroid cancer deaths in the U.S. this year.
Thyroid cancer is more common for certain adults, including women, people with history of thyroid problemsthyroid problems or family history of thyroid cancer, and past radiation exposure (such as radiation treatments to the head and neck).
The National Cancer Institute advises people with a lump or swelling in the neck to see a doctor.
Thyroid Cancer Data
Davies and Welch studied information from death certificates and a database run by the National Cancer Institute.
Among the findings:
- The incidence of thyroid cancer was 3.6 per 100,000 people in 1973.
- The incidence of thyroid cancer was 8.7 per 100,000 people in 2002, a 2.4-fold increase since 1973.
- Papillary thyroid cancer accounted for most of the increase in thyroid cancer incidence.
- No increase was seen in less common thyroid cancers (follicular, medullary, and anaplastic thyroid cancers).
- The U.S. death rate for thyroid cancer was stable from 1973 to 2002, at about 0.5 deaths per 100,000 people.
The National Cancer Institute's database started recording the thyroid tumor size in 1988. From then on, most of the reported tumors were very small. More than eight in 10 were 2 centimeters or less, and nearly half were no bigger than 1 centimeter.
"We believe increased diagnostic scrutiny is the most likely explanation for the apparent increase in incidence," write Davies and Welch.
They note that "advances in imaging and diagnostic techniques" have made it easier to spot thyroid cancerthyroid cancer. The researchers also write that "many of these cancers would likely never have caused symptoms during life."
Further studies should check if "a more cautious diagnostic approach ... is worthwhile," write Davies and Welch. They add that "papillary cancers smaller than one centimeter could be classified as a normal finding."
By definition cancer is not normal, though the study indicates that papillary thyroid cancers may be common and not always show symptoms.
The journal also contains an editorial by Ernest Mazzaferri, MD, of the endocrinology division of the University of Florida at Gainesville.
"The natural history of papillary thyroid cancer plays out over decades," writes Mazzaferri. He adds that current scientific literature includes "reason to believe that not all small [papillary thyroid cancers] are indolent bystanders caught up in a frenzy of excessive diagnosis and unnecessary surgery on small malignant nodules."
Removing the thyroid (with lifelong drug therapy afterward) can eliminate the chance that a tiny papillary thyroid cancer will return, Mazzaferri points out. "It is unlikely that many patients will forgo treatment after receiving this information," he writes.
Mazzaferri is the 2005-2006 president of the American Thyroid Association. His editorial suggests using thyroid imaging and biopsy when thyroid cancer is suspected.